Can anyone tell me which is positive?

Hi.

I am a beginning Mechanical Engineering student and I have this project of building a laser cutter I ordered the parts I needed being the driver, diode, aizix housing..etc only problem I have is that i need to find out which of the pins on the diode is the positive one the one which I need to solder the positive side of the driver I have a small diagram but i really don't understand it and I have done research on how to but couldn't find anything can someone please tell me which are the positive and negative pins based on this diagram thanks!!

Pins 1 and 2 connect to the positive power source.

that means there ir no negative pin?

Pin 3 is the negative terminal.

so if i were to solder the diode onto a driver the positive would be 1 or 2 and negative would be pin 3 right?

That is correct.

thank you alot!!